In recent years the concept of a memristor, originally proposed by Leon Chua in 1971, has generated renewed interest. Chua proposed a forth fundamental component in addition to the three already well known fundamental electronic components: the resistor, capacitor, and inductor. Chua and Kang extended the memristor theory to memristive systems. Memristors and memristive devices are simple two-terminal resistors, where the resistance is changed by the electrical current. The resistance serves as a stored variable.
For almost forty years, the concept of memristors was just theory, as no one produced a component exhibiting the behavior of a memristor. In 2008, Hewlett Packard Laboratories announced that they had succeeded in producing memristors. Since 2008, several possible applications of memristors have been presented. Actually, most emerging memory technologies, including Resistive RAM (RRAM) and Spin-Transfer Torque Magnetoresistive RAM (STT-MRAM) can be considered as memristors. The primary focus of memristor research in academia and industry has been memory. Another interesting application is memristor-based logic.
Material implication (IMPLY) as a memristor-based logic gate was presented. The memristor-based IMPLY logic gate is a natural implementation to be used in a memristive crossbar, which is the structure of commonly used memristive memory (especially for RRAM). The stored data within the memristor is the input and output of the logic gate. This method, however, is not intuitive and requires sequential voltage activation in different locations of the circuit. Furthermore, in IMPLY the result is stored in one of the inputs and not to a dedicated output memristor. The technique also requires extra circuit components (for example, a controller and an additional resistor in each row in the crossbar), dissipates high power, has high computation complexity, and requires complicated control.
There is a growing need to provide an improved memristive device based logic.